Wireless communications, including wireless networks, have become pervasive throughout society. Improvements in wireless communications are vital to increase their reliability and speed. Present wireless communication standards, such as but not limited to, current 802.11a/g and TGnSync proposals, may use pilot locations that are constant over time. Namely, a fixed set of subcarriers may be assigned for pilots for the whole system all the time. This may cause a problem in the presence of platform noise and co-channel narrow band interference. Because the receiver can't gain a synchronization signal from the pilots for a certain period, the receiver's PLL loses synchronization with the transmitter, and thus the packets may get lost.
Extensive measurements demonstrate that mobile platform noise may be a significant factor of WLAN performance degradation. Further, the performance of 802.11a loses more than 20 dB if one of the pilot tones is corrupted by platform noise or co-channel interference of −83 dBm. In contrast, the corruption of data tones with the same interference power only causes a 10 dB lose. Simulation results for 802.11n demonstrate that loss of pilot tones due to fading significantly degrades performance by 0.5-6 dB.
Thus, a strong need exists for techniques to time vary pilot locations in wireless networks.
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